1. Field of the Invention
The present invention relates to an endoscope system comprising an electrically bendable endoscope whose bendable portion is bent via a driving force from driving means, and a bending driving control unit for controlling the driving means.
2. Description of the Related Art
Recently, endoscopes are widely used in the medical field. It is possible to observe a site in a bodily cavity and to apply various treatments on the site by inserting a slender insertion portion of the endoscope into the bodily cavity.
Endoscopes are also used in industrial fields. With the endoscope used in these fields, its insertion portion is inserted into the interior of a boiler, engine, etc., to observe or fix a site.
Generally, the tip end of the insertion portion of such an endoscope includes a bendable portion where is bendable upwards or downward, or leftward or rightward. Inclusion of such bendable portion not only makes it possible for the tip end to more easily pass through a tortuous channel, but also for an optical system attached to the tip end to be more readily directed towards a site to be observed, which will ensure good observation. Bending the bendable portion has been achieved manually or by utilizing a force brought about by a bending motor (to be referred to simply as motor hereinafter).
Among so-called electrically bendable endoscopes (hereinafter referred to as electric endoscope) in which the bendable portion is bent via a force from a motor, some have a joystick in its operation portion as an input feeding means. According to this type of electric endoscopes, the operator instructs the system as to the direction and amount of bending by manipulating the joystick, and the motor is driven according to this instruction. Then, bending effecting wires connected to the bendable portion are pulled, thereby bending the bendable portion in the instructed direction.
According to this electric endoscope, a driving voltage applied to the motor is controlled based on the difference between an instructed bending amount transmitted via the joystick and a value indicated by a potentiometer representing the actual bending amount of the tip end.
Because of this, if the instructed bending amount given via the joystick and the value detected by the potentiometer are very close to each other, a driving force from the motor becomes so small that delicate displacement of the tip end would become impossible.
Further, if the electric endoscope has a long insertion portion to be wound around a drum, and the driving voltage applied to the motor is controlled based on said difference, the bending angle of the bendable portion would vary depending on whether the bending portion is wound around the drum or drawn out from the drum, even if the same bending amount was instructed via the joystick.
Furthermore, with the electric endoscope incorporating a motor-based bending control unit in which instruction regarding a bending amount fed by a bending input feeding means such as a joystick is captured without delay so that the bending amount may serve as a direct reference according to which the motor is controlled to give a desired bending angle, as disclosed, for example, in the U.S. Pat. No. 4,941,454, small fluctuations in the input from the input feeding means will cause the bendable portion to undergo corresponding fluctuated bending. In addition, with this motor-based bending control unit, if there is a difference between the bending amount fed via the bending input feeding means and the actual bent angle of the bendable portion, and the difference is large, the motor might generate a too large force, thereby exposing the bending effecting wire to a too large strain, all the more because the motor is controlled so as to drive and reduce the difference.
An object of the present invention is to provide an endoscope system in which it is possible to securely direct the tip end of an electrically bendable endoscope towards a target site by precisely controlling a driving force applied to a bendable portion of the electrically bendable endoscope.
Another object of the present invention is to provide an endoscope system in which it is possible to reduce strains imposed on bending effecting wires of an electrically bendable endoscope.
The endoscope system of the present invention comprises an electrically bendable endoscope; bending input feeding means for giving an instruction as to a bending amount which includes a bending direction and a bending position; driving means for bending a bendable portion in accordance with a bending instruction signal; detection means for detecting a bent state of the bendable portion; first driving power generating means for generating power necessary for driving the driving means responsible for bending the bendable portion in accordance with a difference between the bending amount instructed via the bending input feeding means and a value given by the detection means representing a bent state of the bendable portion; second driving power generating means for generating pulse driving powers having a predetermined magnitude; and control means for selecting either the first or the second driving power generating means depending on said difference, and driving the driving means using the power therefrom, thereby controlling the bending of the bendable portion. Thus, this system in which the control means controls the action of the driving means based on said difference will ensure that an optimum driving power is selected to operate the driving means.
The above and other objects, features and advantages of the invention will become more clearly understood from the following description based on the accompanying drawings.